1 . Field of the Invention
The invention relates to a method and an apparatus for assessing the residual life of a sensor which is fitted on a cyclically operating machine and is intended for a certain number of loading cycles, the loading cycles of the sensor being counted, and to the application of an apparatus according to the invention on an internal combustion engine.
2 . The Prior Art
Sensors are often fitted on a cyclically operating machine, such as an internal combustion engine or an injection-moulding machine, for example, in order to continuously detect certain measured variables of the machine. Such sensors are subject to natural wear and therefore have a certain life. The life is in this case generally given in a specified permissible number of loading cycles. In this case, a loading cycle is a working cycle, for example a combustion cycle in an internal combustion engine or a casting operation in an injection-moulding machine, which occurs repeatedly. The sensors therefore need to be replaced regularly before they fail or produce results with an insufficiently high quality or accuracy. Until now, the sensors are either replaced after a fixed operating period or the individual loading cycles are simply counted and the sensor is replaced before the specified life has elapsed.
In practice, the life is strongly dependent on the loading of the sensor which actually occurs, however. If the sensor is primarily operated with low loads, the life can be extended. Conversely, the life of the sensor can also be considerably shortened if it is operated to an increased extent on high loads or if it is fitted incorrectly. The sensor can also have loading ranges in which it is subject to more severe damage than in other loading ranges. Life prognoses which are only geared to the number of loading cycles are therefore unreliable. Under certain circumstances, a sensor is replaced which would still have a considerable residual life or would still be suitable for another use, or a sensor fails prematurely.
An object of the invention is therefore to specify a method and an apparatus with which it is possible to assess the residual life of a sensor more precisely but nevertheless easily.